Instrument obsreport.Processor

[moh-osman3]

Description:

This PR instruments obsreport.Processor with otel go. This is a followup PR that is based on similar changes made for obsreport.Receiver: open-telemetry#6222

Link to tracking Issue: Part of open-telemetry#816

Testing:
Ran contrib collector with memory_limiter processor and prometheusreceiver + sent traces from demo client and confirmed that new metrics show up. Tested both with feature gate disabled and enabled.

From output of $ curl localhost:8888/metrics

# HELP otelcol_processor_accepted_metric_points Number of metric points successfully pushed into the next component in the pipeline.
# TYPE otelcol_processor_accepted_metric_points counter
otelcol_processor_accepted_metric_points{processor="memory_limiter",service_instance_id="d957e470-f4a9-4448-b0b9-e2a2e98a2b53",service_name="otelcontribcol",service_version="v0.63.0-48-ge9099f1c57"} 298
# HELP otelcol_processor_accepted_spans Number of spans successfully pushed into the next component in the pipeline.
# TYPE otelcol_processor_accepted_spans counter
otelcol_processor_accepted_spans{processor="memory_limiter",service_instance_id="d957e470-f4a9-4448-b0b9-e2a2e98a2b53",service_name="otelcontribcol",service_version="v0.63.0-48-ge9099f1c57"} 84
# HELP otelcol_processor_dropped_metric_points Number of metric points that were dropped.
# TYPE otelcol_processor_dropped_metric_points counter
otelcol_processor_dropped_metric_points{processor="memory_limiter",service_instance_id="d957e470-f4a9-4448-b0b9-e2a2e98a2b53",service_name="otelcontribcol",service_version="v0.63.0-48-ge9099f1c57"} 0
# HELP otelcol_processor_dropped_spans Number of spans that were dropped.
# TYPE otelcol_processor_dropped_spans counter
otelcol_processor_dropped_spans{processor="memory_limiter",service_instance_id="d957e470-f4a9-4448-b0b9-e2a2e98a2b53",service_name="otelcontribcol",service_version="v0.63.0-48-ge9099f1c57"} 0
# HELP otelcol_processor_refused_metric_points Number of metric points that were rejected by the next component in the pipeline.
# TYPE otelcol_processor_refused_metric_points counter
otelcol_processor_refused_metric_points{processor="memory_limiter",service_instance_id="d957e470-f4a9-4448-b0b9-e2a2e98a2b53",service_name="otelcontribcol",service_version="v0.63.0-48-ge9099f1c57"} 0
# HELP otelcol_processor_refused_spans Number of spans that were rejected by the next component in the pipeline.
# TYPE otelcol_processor_refused_spans counter
otelcol_processor_refused_spans{processor="memory_limiter",service_instance_id="d957e470-f4a9-4448-b0b9-e2a2e98a2b53",service_name="otelcontribcol",service_version="v0.63.0-48-ge9099f1c57"} 0

[jaronoff97]

looks great :D